What is maintenance capex?
- Maintenance capex covers the cost to keep existing equipment and assets working, not to expand.
- You must subtract maintenance capex from net income to get true owner earnings.
- Depreciation is often a rough proxy for maintenance capex, but it's not always accurate.
- Underestimating maintenance capex inflates free cash flow and can mislead investors.
- A simple way to estimate it is to average the company's actual capex over several years and adjust for growth.
What is maintenance capex?
Maintenance capex is the capital expenditures needed to keep a business running, not to grow it, covering repairs and routine upkeep of existing assets. A delivery truck needs tires and brakes; buying a second truck to expand is growth capex.
Total capex splits cleanly into two buckets. Growth capex builds new capacity. Maintenance capex keeps what you already have running. Every dollar lands in one or the other, and the split is where the real story lives.
Why it matters for owner earnings and free cash flow
Owner earnings are the real cash you get from a business after paying for maintenance. If you ignore maintenance capex, you overstate your profit, and that mistake makes a stock look cheaper than it is.
Free cash flow is also hit. Start with operating cash flow, subtract maintenance capex; what's left you can return to shareholders or reinvest. Many companies blur the line, calling growth capex maintenance to make earnings look bigger, so dig into the statements and separate the two yourself.
How to estimate maintenance capex
No company reports maintenance capex directly. You have to estimate it. A common shortcut is to use depreciation as a proxy. Depreciation is the accounting cost of wearing out assets. It is usually close to what you need to maintain them.
Both types live in the cash flow statement under investing activities. Companies rarely label them separately, often just listing additions to property and equipment. The fixed asset schedule in the filings holds the detail you need.
But depreciation is not perfect. If prices rise, replacement costs more than the old book value. So add a bit for inflation. If the company is growing, subtract the extra spend that goes to new capacity.
The depreciation-to-capex ratio reads a company's stage of life. A mature firm's ratio sits near one, roughly 100 percent, its capex just matching depreciation. A ratio far above one means growth is the priority, with heavy expansion spending to come.
A practical method: take the company's total capex over the last five years. Divide by five to get an average. Then subtract the portion that clearly funded growth, like new stores or new factories. What remains is your maintenance capex estimate.
Bruce Greenwald offers a sharper screen: find the ratio of property and equipment to sales over five years, then multiply it by the change in sales. That gives the growth spend to strip out. Check management's own words too, then compare your number to depreciation.
The trap of underestimating maintenance capex
If you skip maintenance capex, you overstate free cash flow and the stock looks cheap, but the real cash is lower. Utilities and airlines often defer maintenance to boost earnings, and a breakdown forces a big write-off, blindsiding investors. Always check whether maintenance spending is growing or postponed.
Some costs refuse to split. Brand advertising keeps current customers but reaches new ones. Research and development both maintains and grows. These sit between the two buckets, so judge them case by case, honestly.
Where maintenance capex matters most
Some industries can never stop reinvesting. Utilities, telecom, airlines, and energy firms must spend constantly just to stand still. Maintenance capex often swallows most of their free cash flow, so the real earnings sit far below the headline.
Dividends expose the lie. When a company pays a payout it cannot cover from true earnings, it borrows from tomorrow. Deferring maintenance to keep cash flowing is not profit, it is spending your capital back to you.
What every investor should know
Warren Buffett calls this owner earnings: net income plus depreciation, minus the money required to keep the business going. He uses it because accounting net income hides what you must actually spend to keep the machine running.
Asset age distorts the picture. A young fleet needs little upkeep, so free cash flow looks rich today. As assets age, maintenance climbs and the free cash you relied on shrinks. Compare maintenance needs to asset age before you trust a high number.